Duplex pump.



Patented Apr. 22, 1919.

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DUPLEX PUMP.

t APPLICATION FILED MAR. I2. |918. l pl ,45% Batented Apr. 22,1919.

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'Patented Apr. 22, 1915).

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DUPLEX PUMP.

APPLICATION FILED MAR. I2. I9I8.

Patented Apr. 22, 1919.

4 SHEETSSHE[T 4 www@ @MTD @AT CHARLES RUSSELL LANG, GF CATHCART, GLASGOW,VSCOTLAND, ASSIGNOR TO G.

WEIR, LIMITED, F CATHCART, GLASGOW, SCOTLAND.

PATNT DUPLEX PUMP.

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Application filed March 12, 1918.

fb @ZZ whom t may concern.'

Be it known that l, 'CHARLES RUSSELL LANG, a subject of the King of Great Britain and Ireland, residing at Cathcart, Glasgow; Scotland, have invented certain new and useful Improvements in Duplex Pumps; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the saine.

This invention relates to pumps of the direct steam-driven duplex type.

The ordinary duplex pump with separate steam and exhaust ports is very wasteful of steam owing to the large clearance volumes. Unless the two pump cylinders are of the same water tightness and have-`-With their steam cylinders and valve driving gearthe same aggregate friction or resistance to motion, short stroking of the stiffer or tighter element is the result. Moreover, if the pump has a suction lift, and the suction pipe is empty of water (as in starting up), it is found that, if steam is turned on with both elements at or about midstroke, the pump will simply dance Vwith each piston reciprocating only a little way on each side of midstroke.

The object of the present invention is to overcome these disadvantages, that is to secure arelatively low steam consumption and to obtain practically the same length of stroke at all speeds and under all conditions.

The invention consists in a construction' valve) controls the admission of steam to the cylinder and also controls the point of release ai. e. opening of exhaust) while the other valve (hereinafter referred to as the exhaust valve) controls the point of cushion or compression (i. e. closing of exhaust). The piston rod of the A element drives a rocking shaft which in turn operates the steam valve of the B cylinder and the exhat'st valve of the A cylinder. The piston rnc et' the E elcmentflrives a rocking Specification of Letters Patent.

Patented Apr. 22, i919.

serial No. 221,986.

shaft which in turn operates the steam valve of the A cylinder and the exhaust valve of the B cylinder. The valves are designed for a movement of each exhaust valve with, and in the same direction, as, the piston of the steam cylinder which it controls (except that the valve may have a certain lost motion which will be hereinafter referred to) and for a movement of each steam valve one-quarter of a cycle, z'. e. about half a stroke, in advance of the piston of the steam cylinder which it controls. As the one steam cylinder works one-quarter of a cycle, z'. e. about half a stroke, in advance of the other cylinder, one of the steam valves must be actuated so as to move in the same direction as the piston rod which drives it, while the other steam valve must be actuated to work in the opposite direction to the pis ton rod which drives it. My invention comprises means for attaining this end.

The steam valves are, according to the present invention, arranged with their axes as close as possible to the axes of the cylinders which they respectively control; and the steam ports are made with as short a length and as small a volume as possible with the object of enabling` the pump to run at a relatively high speed and with relatively low steam consumption.

l-leretofore the steam control valves of duplex pumps (one valve for each steam cylinder) have been arranged with a lost motion in their drive, 'L'. e. the valves have been driven so as to commence their strokes a certain predetermined time after the commencement of the strokes of the pistons which respectively drive them. According to the present invention-which comprises two independent valves for each steam cylinder-each valve may have lost motion and have this lost motion independently adjusted with important results which will be hereinafter stated. y

Moreover, the present invention comprises means whereby, in order to balancethe pressure exerted on the exhaust valves by the steam in the exhaust ports, these valves are arranged with a difference of area back and front in a manner which will be hereinafter described.

Referring now to the accompanying drawings which illustrate my invention p Figure l. is an eleva-tion, partly in section,

steam cylinders, valve castings', and

valve gear of a duplex pump according to my invention.

Fig. 2 is a plan of the same.

Fig. 3 is a vertical section on the line MN of Fig. 2 but showing, in addition, the pump cylinder with its valve casing and valves.

These iigures (1 3) are drawn to the same scale; Figs. il to 9 are drawn to double this scale.

Fig. i is a detail elevation, looking from right to lett, in Fig. 1, ot the mechanism for driving the steam valve of the A (that is left hand) element.

Fig. 5 is a detail elevation looking from right to left in Fig. 1 of the mechanism for driving the steam valve of the B (that is right hand) element and the exhaust valve of the A (that is left hand) element.

Fig. 5 is a vertical section through the steam cylinder and steam valve of the A pump, the section being en the line OP of Fig. 7.

Fig. 7 is a horizontal section on the line QR et Fig. G.

Fig. 8 is a vertical section on the line ST of Fig. 7.

Fig. 9 is a horizontal fseetion ou the line UV of Fig. 8.

Fig. 10 is a diagram showing the relative positions oii'thc main pistons and steam and exhaust valves of the two elements.

Fig. 11 shows a part of a modified mechanism for actuating the valves; it is a detail elevation and a corresponding vieuto Fig. and is drawn to the same scale as that figure.

Fig. 12 shows another part of the same mechanism as Fig. 11; it also is a detail elevation and is drawn to the same .scale as Fig. 1l.

Fig. 13 is a diagram of the saine nature as Fig. 10. It illustrates the relative a-rrangement of main pistons and valves With this modified valve gear drive.

Referring in the first place to Figs. 1-10, i is the steam cylinder of the A (or left hand) element, the steam piston of the same, c the piston and pump rod, f the steam valve, g the steam valve casing, 71y the exhaust valve, j the exhaust valve casing, c the pump cylinder, and d the pump piston. 7c is the steam cylinder of the B (or right hand) element, fn, the steam valve, o the steam valve casing, ,7) the exhaust valve, and g the exhaust valve casing. f1" and s are rocking shafts supported on bearings inthe bracket or other support t carried by the pump framing. The lower shatt s is driven by the :pump rod c of the A element. It drives the exhaust valve li of the A element through the lever g/ (see Figs. 1 and 5) which actuates the valve connecting rod e; and it drives the steam valve a of the B elen'ient through the lever 2 and -the'- doubler armed lever v3, et uhich aetuates` the valve,

connecting rod 5. The lever 2 is keyed on the shaft s and is pivotally connected by the link G With the arm 3 of the two-armed lever 3, i Which is pivotally mounted (that is free to rotate) on the shaft i. The other arm 4 of this double-armed lever actuates t-he valve connecting rod 5. The upper shaft r is driven by the pump rod of the B element. It drives the steam Valve 7 of the A element through the lever u (see Figs. 1, 3, and 4.) which actuates the valve connecting rod and it drives the exhaust valve p of the B element through the lever w (shown only in Fig. 1) which actuates the valve connecting rod y The lever w and valve connecting rod are similar respectively to the lever 7/ and valve connecting rod e (see Fig. 5).

`F 10 represents diagrammatically the relative positions of the main pistons and steam and exhaust vvalves of the tivo elements, the lost mot-ion being ignored. A represents the position of the main piston ot the A element, AS the position of its steam valve, and A, the position of its exhaust valve. B, BS and Be refer similarly to the B element. It Will be noticed firstly y that the B element is one-quarter cycle in advance oi the A element and secondly that, While AS makes its downstreke With B (which drives it) and its upstroke also With B, Bs makes its downstroke With the upstroke of A (which drives it) and its upstrolie with the downstroke of A, that is .AS moves with B, but Bs moves against rin The control et' the steam to, and the exhaust from, the steam cylinder a (of the element A) is as 0lloWs:-Steam is admi-tted by the .port 7 (Fi-gs. 3 and 6) to the interior of the steam valve chest g of the elen'ient A and, When the valve f is at the top of its stroke, the steam enters the cylinder a. by Way of the 4port 8 which is shown in Fig. 6 as covered by the lower end of the valve, but which is uncovered when the valve is at the top of its stroke. This port 8, which is also seen in Fig. 7, is made short and direct so as to enable a relatively low steam consumption and a good cushioning effect to be obtained. The steam valve f (that is A, in Fig. 10) being about half a stroke in advance of the piston 7), the port S is closed by the descent of the valve while the piston Y) is still moving upward, and. before the piston has reached the top of its stroke, the valve has descended sofar that, by means of the chamber 9 formed in its exterior surface, it v.places the port 8 in communication with the passage l0 which leads Vto the port 1l in the casing j of the exhaust valve. The exhaust entering the exhaust valve casing lthrough the ,port 11 escapes therefrom through the port 12 (see Fig. 8). The port 10 remains in communication' with the port 8 during the greater part of the downstroke of the piston 7i but, before the pistoni-caches the bottom of its downstroke, the exhaust valve 7L, which, as shown in Fig. 10, moves with it, closes the port 11 and thus traps a quantity of steam in the cylinder a which acts to eectively cushion the piston at the end of its stroke. Before the piston has reached the bottom of its stroke, the steam valve f has already commenced to move upward and, when the piston is in its lowest position, the port 8 is open to steam. The cycle of operations al-- ready described is then repeated.

The admission of steam to, and exhaust from, the top of the cylinder a and the top and bottom of the steam cylinder of the B element are precisely similar to the action just described.

ln the vconstruction now under consideraation alost motion is introduced in the driving of both steam and both exhaust valves, that is the valves in no case start until the pistons which drive them have advanced a 'certain predetermined fraction of their full stroke. The means for obtaining this lost motion is of a usual nature and can be clearly seen in Fig. 5. The lever 4 is pivotally connected to the block 13 which is free to move up and down on the steam valve connecting rod 5. It actuates the *rod by striking against the adjustable nuts 111, 15, the positions of which on the rod determine the amount of lost motion at one or other end of the stroke of the actuating piston rod. Similarly the lever y is pivotally connected to the block 21 which is free to move up and down on the exhaust valve connecting rod it actuates the rod by engaging with the nuts 2a, 24.

Any device of an equivalent nature could be employed; thespecic means for obtaining the lost motion does not constitute a part of this invention.

By adjusting the lost motion of the exhaust valve, the time of closing of the port 11 (Fig. 8) to exhaust can be adjusted as required, and a similar adjustment made with regard to the closing of the corresponding port at the top of the exhaust valve casing. A cushioning effect exactly as required can therefore be obtained and this without meddling` with the steam valve or altering the point of release.

The shortness and directness of the steam port 8, together with the lost motion of the steam valves, enables the pump to start with a relatively long stroke, and to work with a relatively long stroke even under the most adverse conditions-for example, with a suction lift and with the suction pipe' empty and both elem-ents at about midstroke when starting.

The exhaust valves are given a dierence of area hack andfront by forming a cavity 16 (Figs. 8 and 9) in the exhaust valve face at each end of the valve, a hole 17 being provided establishing communication between this cavity and the interior of the valve. The pressure in the cavity is therefore always that of the interior of the valve, that is exhaust pressure. High pressure steam is admitted by means of the port 1S) to the annular chamber 18 between valve and casing. This high pressure steam gets between the valve and the liner 2() in which it works; and therefore, owing to the exhaust pressure in the cavity 16, there is a dierence of pressure forcing the face of the valve against the liner. which the cavities 16 are formed that controls the ports 11. The pressure on this face brought about by the cavities prevents the face from being blown back from the liner when the cushion or compression pressure exists in the cylinder and presses on the face of the valve through the port 11.

A modified valve gear drive will now be described with reference to Figs. 11, 12, and 13. Fig. 11 shows the driving of the B steam valve and the A exhaust valve, while Fig. 12 shows the driving of the A steam valve and the B exhaust valve.

In the first described arrangement as shown in Fig. 10, the element B is onequarter cycle, z'. e. half a stroke, in advance of the element A ln the modified arrangement, shown in Fig. 13, the element B is one-quarter cycle, z'. e., half a stroke, behind the element A lith this modified drive as in the origi nal, each main piston drives its own exhaust valve in the same direction as itself. In the modied arrangement, however, the B steam valve ascends and descends with the cA piston while the A steam valve ascends with descent of the B piston and descends with ascent of the B piston.

In the modified drive two rocking shafts r and s are employed as before. The means for rocking these shafts is omitted for the sake of clearness but, as before, the lower shaft s is drive-n by the A main piston while the upper shaft r is driven by the B main piston. The shaft s drives the steam valve directly by means of the lever 31, 4which actuates the valve connecting rod 11, while it drives the A exhaust valve by means of the levers and 33 which are pivotally connected to each other by the link 34, the lever 33 being freely mounted on the shaft f1' and arranged to actuate the valve connecting rod 13. The shaft r is placed closer to the of its actuating main piston than in the previously described c'onstruction. This shaft drives the A steam valve directly by means of the lever 36, which actuates the valve connectinfr rod 46, and it drives the B exhaust {va-ve directly by means of lever 37,

It is the face of the valve in the points of admission and cut-cti of steam y and the point of release with respect to that cylinder, a casing for cach valve in which the valve works, an independent valve for each cylinder which controls solely the point of compression with respect to that cylinder,

a casing for `A-each of said latter valves in which the valve works, ports in the casings of each of the said first-mentioned valves beyond the ends of the valves, said ports serving for the adi'nission of steam to the cylinders to which the valves belong, and chambers in the said rst mentioned valves and ports in the casings of the said second mentioned valves, which together and acting in series serve for the exhaust of steam from the cylinders to which the valves belong.

2. A duplex pump having` two steam cylinders, a valve for cach cylinder which controls the points of admission and cut-ott of steam and the oint of release with respect to that eylinc er, an independentvalve for each cylinderwhich controls solely the point of compression with respect to that cylinder7 each valve having a lost motion connection included in its drive, and means for adjusting the said lost motion connections independently tor each of the four valves.

3. A duplex pump havingtwo elements each comprisingl a steam cylinder, a. piston in said cylinder, and a steam valve and an exhaust valve appertaining to said cylinder, one element being a quarter cycle in advance of the' other element, a rocking shaft driven by the piston of the first-named element, a crank on said rocking shaft arranged to drive the exhaust valve of said first-named element in the same direction as the piston of that clement, another crank on said rocking shaft arranged to drive the steam valve of thc second-named element in the same direction as the piston of the first-named element, a rocking shaft driven by the piston of said second-named element, a crank on this roc-king shaft arranged to drive the exhaust valve of the second-named element in the same direction as the iston of that element, another crank on t e last mentioned rocking sha'ft, a two-ar1ned lever freely `nriounted on the Erst mentioned rocking shaft, a link pivotally connecting the last mentioned crank to one arm of the lever while the other arm of the lever is arranged to actuate the steam valve of the iirstnamed element, the last mentioned crank being so arranged with respect to the lever and link that the steam valvey of the first-named element is driven in the reverse direction to the motion of the piston of the sec-ondnamed element.

il. A duplex pump having two steam cylinders, a steam valve appertaining to each cylinder, an exhaust valve appertainin to nach cylinder, a cylindrical casing in w ich each exhaust valve works, a pair of ports in each of said casings, one at each end, said ports being controlled by the face of the valve and serving to admit exhaust steam from the cylinder into the casing beyond the valve, and means for` pressing the face of each exhaust valve on its seat, said means comprising` an annular chamber between the valve and its casing, means for maintaining live steam pressure in said chamber, a pair of cavities in the face of the valve, and means for maintaining exhaust steam pressure in said cavities.

5. A duplex pump, having two steam cyl inders; a valve for each cylinder to control the points of admission and cutoff of steam and the point of release with respect thereto; an independent valve for each cylinder controlling solely the point of compression with respect thereto; a piston working in each cylinder; driving connections between one of said pistons and tlhe secondnamed valve of its cylinder and the first-named valve oli' the other cylinder; and driving connections between the other piston and the second-named valve of the corresponding cylinder and the frstmamed valve of the cylinder first mentioned.

6. A duplex pump, having two steam cylinders; a valve for each cylinder to control the points of admission and cut-o of steam and the point of release with respect thereto; an independent valve for each cylinder controlling solely the point of compression with respect thereto; a piston working in each cylinder; driving connections between one of said pistons and the second-named valve of its cylinder and the hist-named valve of the other cylinder; driving connections between the other piston and the irstnamed valve of the corresponding cylinder and the second-named valve of the cylinder first mentioned; a lost motion device for each valve comprised in said driving connections; and means for adjusting vthe lostmoticn devices independently for eadh of the four valves.

4 7. A duplex pump, having two steam cylinders; al piston arranged in each cylinder, one piston being a quarter-cycle in advance el the other; a rock shaft for each cylinder connected to be driven from the piston thereof; a steam valve and an exhaust valve for each cylinder; a crank secured to each rock shaft and connected to actuate the exhaust valve of the corresponding cylinder in jche same direction as the piston .of that cylinder; a second crank secured to one rock shaft and connected to actuate the steam valve of the corresponding cylinder in the same direction as the piston of that cylinder; a crank loosely mounted on the same rock shaft as the last-named crank and connected to actuate the steam valve of the other cylinder in a direction reverse from that of tlhe piston in said other cylinder; and a second crank secured to the other rock shaft and connected to operate the loose crank.

8. A duplex pump, having two steam cylinders; a valve for each cylinder to control the points of admission and cut-oif of steam, and the point of release with respect thereto; an independent valve for each cylinder controlling solely the point of compression with respect thereto; a piston arranged in each cylinder, one piston being a quartercycle in advance of the other; driving connections between one piston and the secondnamed valve of the corresponding cylinder and the first-named valve of the other cylinder, for actuating said second-named valve in the same direction as that piston, and said tiret-named valve in a direction reverse to that of the other piston; and driving connections between the said other piston and the second-named valve of the corresponding cylinder and tlhe first-named valve of the cylinder first mentioned, for actuating both those valves in the same direction as the pistons of their respective cylinders.

l hereby sign my name to this specification.

CHARLES RUSSELL LANG.

Copies of this patent may be obtained for five cents each, ny addressing the Commissioner of Patents, Washington, D. C. 

